1. Field of the Invention
The present invention relates to a position indicator, having a pen-like shape for example, which is used together with a position detector, and more particularly to a position indicator which has a function of detecting a pressure applied to a tip portion of the position indicator.
2. Description of the Related Art
In recent years, a position input device as an input device has been used in a tablet type personal computer (PC) or the like. The position input device is composed, for example, of a position indicator which is formed so as to have a pen-like shape, and a position detector having an input surface, on which a pointing operation is carried out, characters, figures or the like are inputted, and so forth, by using the position indicator.
FIG. 15 shows an example of a schematic structure of a conventional pen type position indicator 100. The conventional pen type position indicator 100 of this example shown in FIG. 15 is described in Patent Document 1 of Japanese Patent Laid-Open No. 2002-244806, and is used for an electromagnetic induction type position detector. The conventional pen type position indicator 100 of this example includes a resonance circuit, which has a ferrite core 104 and a ferrite chip 102, and which also has one or more resonance capacitors 115 connected to a coil 105 wound around the ferrite core 104.
Although FIG. 15 is a cross sectional view of the position indicator 100, for the sake of clear description, FIG. 15 shows a state in which the coil 105 is wound around the ferrite core 104. As shown in FIG. 15, the conventional pen type position indicator 100 is structured in such a way that the ferrite core 104, around which the coil 105 is wound, and the ferrite chip 102 are made to face each other through an O ring 103, and the ferrite chip 102 comes close to the ferrite core 104 when a pressing pressure (pen pressure) is applied to a core body 101.
It is noted that the O ring 103 is a ring-like elastic member which is obtained by forming an elastic material, such as a synthetic resin or a synthetic rubber, into an O-like shape. In addition, in the position indicator 100, in addition to the constituent elements described above, as shown in FIG. 15, a board holder 113, a board 114, a resonance capacitor 115, a connection line 116 through which the resonance capacitor 115 and the coil 105 are connected to each other, thereby configuring a resonance circuit, a ring type film 117, and a buffer member 118 are accommodated in a hollow chassis (hereinafter simply referred to as “a case”) 111, and positions thereof are fixed by a cap 112.
Also, when the ferrite chip 102 with which the core body 101 composing the pen tip is brought in contact comes close to the ferrite core 104 in accordance with the pressing pressure applied to the core body 101, an inductance of the coil 105 is changed in response to this operation, and thus a phase (resonance frequency) of an electric wave which is transmitted from the coil 105 of the resonance circuit is changed.